Why Do Kettles Get Limescale?

I am sitting here, in my kitchen, sipping on a cup of tea and I'm wondering why do kettles get limescale?

Its an odd thought, this malicious build up in my kettle is something I've never properly looked into. After a bit of research I learned that, kettles get limescale because of a deposit of calcium carbonate and a residue left behind by hard water.

When you heat up hard water at home, in your kettle, the minerals inside the hard water turn into limescale and cling to whatever they can. It lurks inside your kettle as a white crust while staining the interior.

Lets look into what limescale means and the reasons behind it.

How is limescale formed?

It lurks inside most of our kettles at some point but how is limescale actually formed?

The formation of limescale is by and large a consequence of the presence of soluble calcium bicarbonate in water.

Calcium Bicarbonate can decompose when heated to create insoluble calcium carbonate. This is the main component that makes up the large part of limescale.

This process removes temporary hardness from water. Boiling doesn’t work for permanent hardness as the calcium sulfate doesn’t decompose in the same way when heated, so both ions remain in solution.

So, why exactly does limescale form more often on hot surfaces e.g inside our kettle?

Well, according to my research, when heated, carbon dioxide leaves water.

The reaction itself will then try to replace the carbon dioxide in this water inside your kettle.

As more and more carbon dioxide is reformed the more limescale is created.

What is hard water?

Hard water appears to be underlying cause of limescale and what it does to our kettles. Hard water contains a higher concentration of dissolved minerals like calcium and magnesium than normal water. 

For example, water that resides in oceans and streams is hard water as it has already picked up these minerals.

Water that has flown through rocks with calcium sulfate is deemed to be permanently hard.

Which means, when we boil it in our kettle it does not become soft water.

When the hard water evaporates, it leaves behind calcium carbonate deposits. The limescale deposits therefore build up on any surfaces that hard water is in contact with i.e the inside of our kettle. This can accumulate quite quickly when a kettle is frequently used.

Unfortunately, limescale loves to stick to the inside of our kettles and these deposits are a nuisance to remove.

How to test for limescale?

Perhaps you unsure if you actually have limescale in your kettle. Well, we already know that limescale is caused by hard water, so how can we test for it?

To test to see if you have hard water, you can try a quick home soap lather test.

Put a small amount of household soap into any bottle and fill it halfway with water.

Once shaken, if you have frothy, bubbly water, you are most likely in the clear and your kettle has soft water.

However, If you have cloudy or milky water with bubbles, you most likely have hard water in your kettle. If you suspect you have hard water, you can use a water softener test kit at to assimilate the accurate hardness of your water.

How can I remove limescale in my kettle?

If you are certain that your kettle contains limescale, there are some recommended removal methods that I've found. However, its important to not attempt to remove limescale from a kettle like you would for other limestone affected appliances.

This is because any substance that will be used for removal will remain inside your kettle and may affect how drinkable your boiled water is.

The process of removing limescale from a kettle is known as descaling.

Limescale can generally be dissolved with a range of mildly acidic home items.

Here are some suitable methods I found for removing limescale in a kettle:

Vinegar/Lemon

You can clean your kettle with vinegar, by boiling the kettle with a solution ½ vinegar(or lemon) and ½ water, and then giving the areas tainted with limescale a scrub.

Here is a video with more detailed instructions:

Alternatively, you can start the kettle to a boil, turn it off and allow the water and vinegar mixture to settle in the kettle for 15 to 20 minutes. Ensure that the water and vinegar are discarded after use.

Citric Acid

Most citric based acids seem to be very effective on limescale.

Fill your kettle halfway with water, and bring it to a boil.

Once it has boiled, turn it off and add 1 – 2 tablespoons of citric acid power to the water.

Let the water and citric mixture settle in the kettle for 15 to 20 minutes, then empty the contents.

Removing this limescale can extend the life of your kettle. It can also remove some unpleasant tastes that are in your boiled water as a result of existing limescale.

Is limescale bad for you?

Before researching this, I thought that this would be the most contentious part on the topic of limescale.

As we are consuming the water from our kettles it is probably the most essential piece of information needed.

However, the results I found seem to be largely positive. It is generally thought that water that is either hard or soft is deemed safe to drink provided that it has gone through the correct treatment plant.

Studies

I found an article from the BBC stating that Hard water 'stops heart attacks' , however, that article is from 2004 and should be taken with a pinch of salt.

The WHO(world health organisation) published a comprehensive document on hard water. It states that:

In the conclusion of this document, no health-based guideline value for water hardness were proposed.

Taste

While not an indication of being bad for you, a limescale issue inside a kettle can definitely change the taste and consistency of the water used for a hot brew.

In my experience, the water has a metallic taste which is far from ideal but easily solvable by the following methods of prevention.

How can I prevent limescale in my kettle?

I found a few recommended measures for preventing limescale in your kettle.

Rinsing

The easiest is by simply rinsing out the contents of your kettle and drying it. This will prevent the buildup of limescale that occurred from hard water use.

However, this does not seem convenient. Who has the time to do this considering how often you may make a hot brew?

Water Softener

A more convenient solution would be to purchase a water softener. A water softener transforms hard water into soft water. It does this by removing the concentration of minerals like calcium and magnesium.

This seems to significantly reduce the overall build up limescale.

Purify Water

A more cumbersome solution is not use any hard water at all. This can be achieved by using a water filter or water purifier beforehand.

This ensures that the water being put into your kettle will always be soft water and you will completely avoid the problem altogether.

However, this is not sufficient solution for everyone as some regions have harder water than others therefore making it difficult to purify that water.

If in a hurry, you might not have purified water ready to go.

Some kettles include this limescale filter as the water goes in. This is a great solution for those on a hectic schedule.

Overall Benefits

Limescale inhibits the ability for our kettles to run at full efficiency. Implementing some of these preventive measures mentioned will ensure the longevity of your kettle.

As a result of the heavy presence of limescale, the power consumption of the kettle increases as more power is required to heat the water to boiling temperature.

Not only is this inefficient for your kettle but requires more electricity to power the boiling process. This increases the cost of heating your water.

The kettles heating capabilities can deteriorate gradually because of this.

But limescale might be an indicator of a bigger issue. Even though it can be easily removed from your kettle, the build of limescale is a strong indicator of hard water present in your household water system.

Depending on the water composition of calcium and magnesium  This might need further examination.

Overall, this research has taught me that there is a lot more depth to heating water than I would have imagined. And limescale can be a huge deciding factor in creating the perfect hot brew with your kettle.